Beryllium-10 surface exposure dating of offset moraines on one branch of the Karakorum Fault west of the Gar basin yields a long-term (140- to 20-thousand-year) right-lateral slip rate of similar to10.7 +/- 0.7 millimeters per year. This rate is 10 times larger than that inferred from recent InSAR analyses (similar to1 +/- 3 millimeters per year) that span similar to8 years and sample all branches of the fault. The difference in slip-rate determinations suggests-that large rate fluctuations may exist over centennial or millennial time scales. Such fluctuations would be consistent with mechanical coupling between the seismogenic, brittle-creep, and ductile shear sections of faults that reach deep into the crust.